Check example images for diffuse comparison. Their color balance was perfect for BC1 compression so artifacts can be hard to spot.
Normal map reduced to half size obviously reduces quality, but I can't tell the difference in game at 1080p. Trust my eyeballs or help Abhorrent Behemoths with their skin care routine.


Abhorrent Behemoths

Original textures were 4k.
Diffuse same resolution compressed with BC1. 1/2 file size.
Normal reduced to half resolution and compressed with BC7. 1/4 file size.


Anthropoid Daedroths

Original textures were 4k
Diffuse same resolution compressed with BC1. 1/2 file size.
Normal reduced to half resolution and compressed with BC7. 1/4 file size.


Bipedal Charyboids

Original textures were 4k
Diffuse same resolution compressed with BC1. 2/3 file size.*
Other diffuse same resolution compressed with BC1. 1/2 file size.**
Normal reduced to half resolution and compressed with BC7. 2/3 file size.***

*Original was smaller than other diffuse, possibly because of missing mipmaps. GIMP could not open original texture so I couldn't check. Both diffuses are same size with mipmaps now.
**This one (1_Albedo.dda) is less suited to BC1 so more visible artifacts. See blue example images.
***Again original was possibly missing mipmaps.


Fire Tongued Daedroths

Diffuse (_Albedo.dds) same resolution, generated mipmaps, compressed with BC1. 2/3 file size.
Diffuse (Albedo_1.dds) reduced from 8k to 4k, compressed with BC1. 1/8 file size.
Normal (_Normal.dds) reduced from 4k to 2k, generated mipmaps, compressed with BC7. 1/3 file size.
Normal (_Normal_1.dds) reduced from 8k to 2k, compresesd with BC7. 1/16 file size.